A Robotic Game Changer for the Replacement of UK Gas Distribution Networks

"We hit key milestones on time to ensure funding continued to drive this innovation. LabVIEW software, the Vision Development Module, and access to NI Alliance Partners helped us ensure reduced software development time compared to other means, with a visually stunning end result. "

Replacing aged gas cast iron mains and services involves excavating the ground to expose the main and safely cut off the gas supply. This usually is done in sections along an urban street. Each customer service to be connected to the recommissioned main requires further excavation. Workers must insert the old iron main with a section of new polyethylene (PE) pipe. At each service connection, workers deliberately break the main to expose the PE pipe and fuse a PE saddle in place. They insert a new PE service pipe into the old metal pipe from the garden of the property towards the new PE main and then fuse it through the PE saddle. They complete the operation by inserting a PE pipe from the customer gas meter and connect it with a mechanical fitting at an excavation in the garden. They pressure test and recommission the completed section of replaced main and connections, then they reinstate the ground. Typically, 10 houses are off gas this time. Each service requires two excavations per service and an excavation at each end of the main. Therefore, 22 excavations are necessary, which makes the complete process costly and disruptive to the customer.

Synthotech Limited is a leading UK SME engineering company focused on the development of pioneering products and services for utility and infrastructure markets around the world. Over three years, Synthotech and National Grid Gas developed the TORS Robotic Platform using the OFGEM Network Innovation Allowance funding to take a concept to reality through six stage gates. The first three stages focus on developing two working concepts (for pipe diameters of 250 mm and 90 mm), then a detailed feasibility investigation into establishing a technological solution to facilitate the remote connection of a replaced PE service and a PE replacement main inserted within a metallic carrier pipe. The feasibility study demonstrated how we could use a plug-and-play articulated robot for the effective renewal of gas mains and services. Such a solution would mean that a significant length of street could be reconnected through only two excavations, one at each end of the section of old cast iron main. The result would reduce costs and resources required significantly, whilst improving safety, reducing environmental impact through reduced waste to landfills, and reducing customer and third party disruption. All of this would lead to greater customer satisfaction.

Hardware Implementation

The current stage of the TORS Project (Stage 4) has focused on the development of working prototypes, moving from 3D printing into complex CNC and subtractive manufacture. The complete robotic system consists of a mobile embedded controller, about 100 m of robotic tether, and several robotic modules. The bespoke robotic modules are all based on a common architecture (SMoREs) for vast scalability, modularity, and extensibility as well as project risk mitigation.

Figure 2. Individual Robotic Modules

The main replacement process includes several steps with a robotic module to complete each separate task. The minimum space within the inserted PE main for the robotics modules is 55 mm in diameter. This space limitation forced us to develop bespoke embedded electronics and pneumatics hardware. The communication between the modules and controller uses an RS485 serial protocol, which delivers on-the-fly manipulation of baud rate up to a maximum of 28,800 bps. This offers flexibility in the future for developments like short distance, high-speed operation and long-distance application of the robotic modules, whilst still using standard NI products.

The hardware currently consists of nine modules that, due to the size limitations, contain 90 percent bespoke components. Generic control sections that contain common electronic and pneumatic hardware miniaturised and optimised over the development cycle power and control all the individual modules.

Software Implementation

To help deliver software to control the robot, we sought the help of our technology partner and NI Alliance Partner, Key Engineering Solutions. For a number of years Key Engineering Solutions has demonstrated its capability in applying innovative thinking to solve the most challenging robotic and automated industrial problems.

We designed the modular robot to be fully scalable and configurable to meet the varying requirements of the job. Software to drive the TORS robot had to interact with and control a multitude of varying hardware, as well as process and present information in real time to the user in an informative manner. This presented two main challenges: first, how to architecturally meet the needs of such a dynamic system, and second, how to develop local and global intelligence for the system to effectively drive itself.

We decoupled hardware into modules that could be independently run in parallel at optimal rates. Then we used a producer/consumer software architecture to control execution flow of the parallel tasks. To complement the truly plug-and-play nature of the TORS robot, we adopted a plug-in methodology for the control of each individual articulation that is connected together by the user. This approach required writing a separate stand-alone piece of code (a plug-in) for each type of robotic module. We could then run these dynamically by the main software when needed to control a specific articulation of a module.

Crucial to our methodology was a module discovery algorithm that we used to ascertain which modules are connected together to form the robot and in what order. The software can then access plug-ins from the bank available and run them dynamically in an order to mirror that of the hardware arrangement. The approach is also fully scalable with TORS developments. As we create new robotic modules, we can develop a corresponding software plug-in from a template. We can then simply place it into a plug-in folder, alongside existing articulation plug-ins, where it can be dynamically loaded if needed.

Figure 3. Developed Electronics Figure 4. Modular Connector

Intelligence within the software delivers a two-level approach: first, at a local level, algorithms within the plug-ins specific to the current active module (for example, drill), and second, at global level by the plug-ins feeding information back to the event handler, which can then make decisions and control execution flow order of the whole robot. We can address and control modules of the same type (for example, drive) to perform a task on a broadcast or an individual basis. We then achieved full autonomy of the system through the combined use of vision and PID control. Various image processing and detection algorithms developed using the NI Vision Development Module analyse two video streams, which are selected from the matrix of onboard cameras at 30 fps, with a resolution of 640 x 480. Output from the process feeds PID controllers to drive the robot for optimal alignment for various jobs like welding. The vision system also forms part of quality control for task and job records. Following the completion of a task, the user is notified of its success and then given options to perform the next steps.

Conclusion

We developed and demonstrated as a bench top prototype to NGG an alternative and innovative method of mains/service pipe renewal. The system is truly plug-and-play and is configurable and scalable to adapt to the job at hand. The solution means that significant lengths of street can be reconnected through only two single excavations. Typically this means one excavation at each end of the length of street being worked on, which corresponds to significantly lower operational costs, improved safety, environmental benefits, and reduced disruption.

We hit key milestones on time to ensure funding continued to drive this innovation. LabVIEW software, the Vision Development Module, and access to NI Alliance Partners helped us ensure reduced software development time compared to other means, with a visually stunning end result.

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